The passage is in the Ratzinger 1955 Bonaventure thesis in the section on Bonaventure's theory of man's natural desire for the supernatural (part of what I like to call the distinctive eternal instinct of man). Here is a very melodic quote of Bonaventure's prose on the matter, saying that even after The Fall, the divine orientation of man persists.
"Sic enim cecidit a rectitudinem, ut perderet habitum, non appetitum: quia sic amittit similitudinem, ut tamen pertranseat in imaginem (Ps 38:7)". Note 112. Prooem in II Sent (II 5 b).
--Ratzinger, Obras Completas II, 237.
I would say that this thought is at the heart of Pope Francis' confusion regarding morality. He is confusing anthropology with morality. He talks about the inherent dignity of man and transposes that indelible worth to the realm of morality. The problem is that man, though oriented toward God by nature, can contradict that orientation and thereby break divine friendship by his actions: viz. fall from Grace.
Indeed, every man in mortal sin continues to be a man, imago Dei/capax Dei, destined for divine beatitude, though he deprives himself of that inheritance by his sins.
Our proper disposition toward that sinner is to work and hope for his conversion to regain his fallen status. "Hate the sin but love the sinner," and, without denying the real existential depravity of the sinner in his fallen state. He needs repentance, he needs the love of Jesus, he needs to love Jesus to regain himself! He has alienated himself from God and from the Church by his sin. That is the ontological reality of his moral state, which does not at all, of course, deprive him of his status as man: e.g. the prodigal son remembers his place in his father's house, though he was far away. When he recalls his dignity he regains it, by the mercy of the father! But he must recall/retrieve his dignity for it to be effective for him. He had to decide to come back!